/* Respond.js: min/max-width media query polyfill. (c) Scott Jehl. MIT Lic. j.mp/respondjs  */
(function (w) {

	"use strict";

	//exposed namespace
	var respond = {};
	w.respond = respond;

	//define update even in native-mq-supporting browsers, to avoid errors
	respond.update = function () {
	};

	//define ajax obj
	var requestQueue = [],
			xmlHttp = (function () {
				var xmlhttpmethod = false;
				try {
					xmlhttpmethod = new w.XMLHttpRequest();
				}
				catch (e) {
					xmlhttpmethod = new w.ActiveXObject("Microsoft.XMLHTTP");
				}
				return function () {
					return xmlhttpmethod;
				};
			})(),

	//tweaked Ajax functions from Quirksmode
			ajax = function (url, callback) {
				var req = xmlHttp();
				if (!req) {
					return;
				}
				req.open("GET", url, true);
				req.onreadystatechange = function () {
					if (req.readyState !== 4 || req.status !== 200 && req.status !== 304) {
						return;
					}
					callback(req.responseText);
				};
				if (req.readyState === 4) {
					return;
				}
				req.send(null);
			},
			isUnsupportedMediaQuery = function (query) {
				return query.replace(respond.regex.minmaxwh, '').match(respond.regex.other);
			};

	//expose for testing
	respond.ajax = ajax;
	respond.queue = requestQueue;
	respond.unsupportedmq = isUnsupportedMediaQuery;
	respond.regex = {
		media: /@media[^\{]+\{([^\{\}]*\{[^\}\{]*\})+/gi,
		keyframes: /@(?:\-(?:o|moz|webkit)\-)?keyframes[^\{]+\{(?:[^\{\}]*\{[^\}\{]*\})+[^\}]*\}/gi,
		comments: /\/\*[^*]*\*+([^/][^*]*\*+)*\//gi,
		urls: /(url\()['"]?([^\/\)'"][^:\)'"]+)['"]?(\))/g,
		findStyles: /@media *([^\{]+)\{([\S\s]+?)$/,
		only: /(only\s+)?([a-zA-Z]+)\s?/,
		minw: /\(\s*min\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
		maxw: /\(\s*max\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
		minmaxwh: /\(\s*m(in|ax)\-(height|width)\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/gi,
		other: /\([^\)]*\)/g
	};

	//expose media query support flag for external use
	respond.mediaQueriesSupported = w.matchMedia && w.matchMedia("only all") !== null && w.matchMedia("only all").matches;

	//if media queries are supported, exit here
	if (respond.mediaQueriesSupported) {
		return;
	}

	//define vars
	var doc = w.document,
			docElem = doc.documentElement,
			mediastyles = [],
			rules = [],
			appendedEls = [],
			parsedSheets = {},
			resizeThrottle = 30,
			head = doc.getElementsByTagName("head")[0] || docElem,
			base = doc.getElementsByTagName("base")[0],
			links = head.getElementsByTagName("link"),

			lastCall,
			resizeDefer,

	//cached container for 1em value, populated the first time it's needed
			eminpx,

	// returns the value of 1em in pixels
			getEmValue = function () {
				var ret,
						div = doc.createElement('div'),
						body = doc.body,
						originalHTMLFontSize = docElem.style.fontSize,
						originalBodyFontSize = body && body.style.fontSize,
						fakeUsed = false;

				div.style.cssText = "position:absolute;font-size:1em;width:1em";

				if (!body) {
					body = fakeUsed = doc.createElement("body");
					body.style.background = "none";
				}

				// 1em in a media query is the value of the default font size of the browser
				// reset docElem and body to ensure the correct value is returned
				docElem.style.fontSize = "100%";
				body.style.fontSize = "100%";

				body.appendChild(div);

				if (fakeUsed) {
					docElem.insertBefore(body, docElem.firstChild);
				}

				ret = div.offsetWidth;

				if (fakeUsed) {
					docElem.removeChild(body);
				}
				else {
					body.removeChild(div);
				}

				// restore the original values
				docElem.style.fontSize = originalHTMLFontSize;
				if (originalBodyFontSize) {
					body.style.fontSize = originalBodyFontSize;
				}


				//also update eminpx before returning
				ret = eminpx = parseFloat(ret);

				return ret;
			},

	//enable/disable styles
			applyMedia = function (fromResize) {
				var name = "clientWidth",
						docElemProp = docElem[name],
						currWidth = doc.compatMode === "CSS1Compat" && docElemProp || doc.body[name] || docElemProp,
						styleBlocks = {},
						lastLink = links[links.length - 1],
						now = (new Date()).getTime();

				//throttle resize calls
				if (fromResize && lastCall && now - lastCall < resizeThrottle) {
					w.clearTimeout(resizeDefer);
					resizeDefer = w.setTimeout(applyMedia, resizeThrottle);
					return;
				}
				else {
					lastCall = now;
				}

				for (var i in mediastyles) {
					if (mediastyles.hasOwnProperty(i)) {
						var thisstyle = mediastyles[i],
								min = thisstyle.minw,
								max = thisstyle.maxw,
								minnull = min === null,
								maxnull = max === null,
								em = "em";

						if (!!min) {
							min = parseFloat(min) * ( min.indexOf(em) > -1 ? ( eminpx || getEmValue() ) : 1 );
						}
						if (!!max) {
							max = parseFloat(max) * ( max.indexOf(em) > -1 ? ( eminpx || getEmValue() ) : 1 );
						}

						// if there's no media query at all (the () part), or min or max is not null, and if either is present, they're true
						if (!thisstyle.hasquery || ( !minnull || !maxnull ) && ( minnull || currWidth >= min ) && ( maxnull || currWidth <= max )) {
							if (!styleBlocks[thisstyle.media]) {
								styleBlocks[thisstyle.media] = [];
							}
							styleBlocks[thisstyle.media].push(rules[thisstyle.rules]);
						}
					}
				}

				//remove any existing respond style element(s)
				for (var j in appendedEls) {
					if (appendedEls.hasOwnProperty(j)) {
						if (appendedEls[j] && appendedEls[j].parentNode === head) {
							head.removeChild(appendedEls[j]);
						}
					}
				}
				appendedEls.length = 0;

				//inject active styles, grouped by media type
				for (var k in styleBlocks) {
					if (styleBlocks.hasOwnProperty(k)) {
						var ss = doc.createElement("style"),
								css = styleBlocks[k].join("\n");

						ss.type = "text/css";
						ss.media = k;

						//originally, ss was appended to a documentFragment and sheets were appended in bulk.
						//this caused crashes in IE in a number of circumstances, such as when the HTML element had a bg image set, so appending beforehand seems best. Thanks to @dvelyk for the initial research on this one!
						head.insertBefore(ss, lastLink.nextSibling);

						if (ss.styleSheet) {
							ss.styleSheet.cssText = css;
						}
						else {
							ss.appendChild(doc.createTextNode(css));
						}

						//push to appendedEls to track for later removal
						appendedEls.push(ss);
					}
				}
			},
	//find media blocks in css text, convert to style blocks
			translate = function (styles, href, media) {
				var qs = styles.replace(respond.regex.comments, '')
						.replace(respond.regex.keyframes, '')
						.match(respond.regex.media),
						ql = qs && qs.length || 0;

				//try to get CSS path
				href = href.substring(0, href.lastIndexOf("/"));

				var repUrls = function (css) {
							return css.replace(respond.regex.urls, "$1" + href + "$2$3");
						},
						useMedia = !ql && media;

				//if path exists, tack on trailing slash
				if (href.length) {
					href += "/";
				}

				//if no internal queries exist, but media attr does, use that
				//note: this currently lacks support for situations where a media attr is specified on a link AND
				//its associated stylesheet has internal CSS media queries.
				//In those cases, the media attribute will currently be ignored.
				if (useMedia) {
					ql = 1;
				}

				for (var i = 0; i < ql; i++) {
					var fullq, thisq, eachq, eql;

					//media attr
					if (useMedia) {
						fullq = media;
						rules.push(repUrls(styles));
					}
					//parse for styles
					else {
						fullq = qs[i].match(respond.regex.findStyles) && RegExp.$1;
						rules.push(RegExp.$2 && repUrls(RegExp.$2));
					}

					eachq = fullq.split(",");
					eql = eachq.length;

					for (var j = 0; j < eql; j++) {
						thisq = eachq[j];

						if (isUnsupportedMediaQuery(thisq)) {
							continue;
						}

						mediastyles.push({
							media: thisq.split("(")[0].match(respond.regex.only) && RegExp.$2 || "all",
							rules: rules.length - 1,
							hasquery: thisq.indexOf("(") > -1,
							minw: thisq.match(respond.regex.minw) && parseFloat(RegExp.$1) + ( RegExp.$2 || "" ),
							maxw: thisq.match(respond.regex.maxw) && parseFloat(RegExp.$1) + ( RegExp.$2 || "" )
						});
					}
				}

				applyMedia();
			},

	//recurse through request queue, get css text
			makeRequests = function () {
				if (requestQueue.length) {
					var thisRequest = requestQueue.shift();

					ajax(thisRequest.href, function (styles) {
						translate(styles, thisRequest.href, thisRequest.media);
						parsedSheets[thisRequest.href] = true;

						// by wrapping recursive function call in setTimeout
						// we prevent "Stack overflow" error in IE7
						w.setTimeout(function () {
							makeRequests();
						}, 0);
					});
				}
			},

	//loop stylesheets, send text content to translate
			ripCSS = function () {

				for (var i = 0; i < links.length; i++) {
					var sheet = links[i],
							href = sheet.href,
							media = sheet.media,
							isCSS = sheet.rel && sheet.rel.toLowerCase() === "stylesheet";

					//only links plz and prevent re-parsing
					if (!!href && isCSS && !parsedSheets[href]) {
						// selectivizr exposes css through the rawCssText expando
						if (sheet.styleSheet && sheet.styleSheet.rawCssText) {
							translate(sheet.styleSheet.rawCssText, href, media);
							parsedSheets[href] = true;
						} else {
							if ((!/^([a-zA-Z:]*\/\/)/.test(href) && !base) ||
									href.replace(RegExp.$1, "").split("/")[0] === w.location.host) {
								// IE7 doesn't handle urls that start with '//' for ajax request
								// manually add in the protocol
								if (href.substring(0, 2) === "//") {
									href = w.location.protocol + href;
								}
								requestQueue.push({
									href: href,
									media: media
								});
							}
						}
					}
				}
				makeRequests();
			};

	//translate CSS
	ripCSS();

	//expose update for re-running respond later on
	respond.update = ripCSS;

	//expose getEmValue
	respond.getEmValue = getEmValue;

	//adjust on resize
	function callMedia() {
		applyMedia(true);
	}

	if (w.addEventListener) {
		w.addEventListener("resize", callMedia, false);
	}
	else if (w.attachEvent) {
		w.attachEvent("onresize", callMedia);
	}
})(this);
